A quantitative discharge device for discharging fluid from a discharge side of a container at a predetermined rate while pressurizing the fluid in the container is applicable to fluids of a wide range of viscosities from water (a low viscous fluid) to a paste-like highly viscous fluid. The device can discharge a desired quantity of fluid from a very small quantity to a very large quantity. For that reason, the range of application of the device is very wide, and the device can properly cope with various working processes such as drip and sealing, coating, filling, etc. and is used in the manufacture of electronics, container filling and many other fields of industry.
In the conventional quantitative discharge device, the rate of fluid discharge is controlled using a certain discharge time and a certain discharge air pressure, and the quantity of fluid within the container is decreased with the progress of discharge work while the volume of compressed air in the container is correspondingly increased. The discharge air pressure is gradually reduced in inverse proportion to the increase in volume of such compressed air and discharge accuracy of the quantitative discharge device deteriorates. As a result, the quantitative discharge is not performed satisfactorily.
In order to avoid this inconvenience, the present applicant has already developed a device for automatically controlling and changing the air pressure applied to the fluid and/or the discharge time of the fluid, thereby to realize the desired quantitative discharge.
However, it does not disclose the mounting position of the pressure sensor for detecting air pressure at the time when the fluid is discharged, and discharge characteristics of an apparatus for controlling pressure change type discharge rate stabilization dispense, which are available depending on the mounting position of the pressure sensor, cannot be achieved.
Therefore, in an attempt to obviate the above-mentioned inconvenience and improve upon the present applicant's aforementioned device, the present invention provides a dispense control apparatus for stably controlling a pressure change type fluid discharge rate of a quantitative discharge device, such dispense control apparatus having a pressure sensor. The dispense control apparatus comprises a keyboard for inputting signals for effecting initialization and discharge, a microcomputer for receiving signals from the keyboard for effecting initialization and discharge, an interface for receiving a digital pressure command signal from said microcomputer, an electropneumatic regulator for receiving an analog pressure command signal from said interface, a solenoid valve disposed in a middle part of an air channel of said electropneumatic regulator, and a pressure sensor for detecting discharge air pressure of acting on the fluid, said pressure sensor being disposed so as to be able to detect discharge air pressure at the time when the fluid is discharged from said quantitative discharge device, whereby discharge characteristics of said apparatus are disclosed. The mounting position of said pressure sensor can be established depending on the fluid, and much easier handling is ensured.
With the aforementioned arrangement, discharge air pressure is detected by the pressure sensor at the time when the fluid is discharged from the quantitative discharge device. Then a calculation is made by the dispense control apparatus in accordance with pressure and time signals produced while the fluid is being discharged, and the undesirable reduction of the fluid discharge rate caused by reduction of fluid quantity during fluid discharge is automatically avoided by controlling and stabilizing the discharge rate of the fluid, thereby achieving the desired quantitative discharge.